Abstract
Background: Despite the popularity of functional connectivity analyses and the well-known topology of several intrinsic cortical networks, relatively little is known about the white matter regions (i.e., structural connectivity) underlying these networks. In the current study, we have therefore performed fMRI-guided diffusion tensor imaging (DTI) tractography to create probabilistic white matter atlases for eight previously identified functional brain networks, including the Auditory, Basal Ganglia, Language, Precuneus, Sensorimotor, Primary Visual, Higher Visual and Visuospatial Networks.Methods: Whole-brain diffusion imaging data were acquired from a cohort of 32 healthy volunteers, and were warped to the ICBM template using a two-stage, high-dimensional, non-linear spatial normalization procedure. Deterministic tractography, with fractional anisotropy (FA) ≥0.15 and deviation angle <50°, was then performed using the Fiber Association by Continuous Tracking (FACT) algorithm, and a multi-ROI approach to identify tracts of interest. Regions-of-interest (ROIs) for each of the eight networks were taken from a pre-existing atlas of functionally defined regions to explore all ROI-to-ROI connections within each network, and all resulting streamlines were saved as binary masks to create probabilistic atlases (across participants) for tracts between each ROI-to-ROI pair.Results: The resulting functionally-defined white matter atlases (i.e., for each tract and each network as a whole) were saved as NIFTI images in stereotaxic ICBM coordinates, and have been added to the UManitoba-JHU Functionally-Defined Human White Matter Atlas (http://www.nitrc.org/projects/uofm_jhu_atlas/).Conclusion: To the best of our knowledge, this work represents the first attempt to comprehensively identify and map white matter connectomes for the Auditory, Basal Ganglia, Language, Precuneus, Sensorimotor, Primary Visual, Higher Visual and Visuospatial Networks. Therefore, the resulting probabilistic atlases represent a unique tool for future neuroimaging studies wishing to ascribe voxel-wise or ROI-based changes (i.e., in DTI or other quantitative white matter imaging signals) to these functional brain networks.
Highlights
Cerebral white matter is comprised of myelinated axons that transmit signals between different brain regions, and the importance of these connections is underscored by the severe and wide-spread deficits that arise when they are compromised
Since no connections were found to meet this threshold in the Auditory Network (AN) or Primary Visual Network (PVN), no probabilistic atlases were generated for these networks
The current study expands on that effort by including comprehensive white matter maps of the Basal Ganglia Network (BGN), Language Network (LN), Precuneus Network (PN), Sensorimotor Network (SMN), Higher Visual Network (HVN) and Visuospatial Network (VSN)
Summary
Cerebral white matter is comprised of myelinated axons that transmit signals between different brain regions, and the importance of these connections is underscored by the severe and wide-spread deficits that arise when they are compromised (e.g., due to traumatic injury, stroke or disorders such as Multiple Sclerosis; Filley, 1998; Schmahmann et al, 2008). Unlike the gray matter, which has been well mapped, relatively little is known about white matter topology or how particular white matter regions (or sets of regions) correspond to specific brain functions. Even in highly-parcellated white matter atlases (such as the aforementioned JHU Eve Atlas), many of the ROIs are relatively large. As a corollary of the aforementioned limitations, there is a high likelihood that some of the larger anatomically-defined ROIs will span white matter regions underlying multiple neural functions—meaning that even if white matter differences are observed, they may not correspond to differences in specific behaviors, symptoms, or deficits. Despite the popularity of functional connectivity analyses and the well-known topology of several intrinsic cortical networks, relatively little is known about the white matter regions (i.e., structural connectivity) underlying these networks. We have performed fMRI-guided diffusion tensor imaging (DTI) tractography to create probabilistic white matter atlases for eight previously identified functional brain networks, including the Auditory, Basal Ganglia, Language, Precuneus, Sensorimotor, Primary Visual, Higher Visual and Visuospatial Networks
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